Dispensers for continuous, unperforated flexible sheet material, such as paper toweling, include those in which the sheets are simply torn from the web by the user or, more commonly, those in which the sheets are completely severed by a cutter in the dispenser for removal by a user. Also known are dispensers in which the cutter in the dispenser produces a line of cuts including residual segments of uncut material in the web defining the desired sheet that is, thereafter, completely severed by the user upon removal.
Dispensers of more recent design utilize cutting devices in the dispenser that cut the web material to sheet length as the user pulls it from the dispenser. Such apparatus typically involve a feed roll from which paper is supplied by a user grasping the free end of the web that is disposed outside the dispenser chassis and pulling it to operate the feed roll. In these devices a stored energy mechanism, such as a spring, may be associated with the feed roll to activate the cutter and/or to conduct the web material from the dispenser. As mentioned, cutters for such dispensers may cut the material to totally sever a sheet from the web or, alternatively, may produce such a cut as will only partially sever the web, leaving the sheet connected to the web by means of one or more unsevered segments of residual web material, for removal by the user following conduct of the sheet from the dispenser by the feed roll.
Dispensers of the concerned type in which a cutter operates in conjunction with a feed roll and in which the motive force for the operation of the dispenser is provided by the web material being pulled by the user are exemplified by U.S. Pat. Nos. 3,575,328; 4,122,738; 4,621,755 and 5,441,189. These dispensers each characteristically employ an over-center spring drive that is loaded during a first portion of the operating cycle of the mechanism during which cutting is normally effected as the web material, in friction contact with the feed roll, is pulled from the dispenser. After completion of the cutting operation, when the feed roll is rotated beyond the over-center condition, the spring is unloaded and the energy stored therein is utilized to drive the feed roll to conduct the cut web portion from the dispenser and to dispose the leading end of the succeeding length of web material at a location outside the dispenser chassis where it can be readily grasped by the next user.
In the mechanism described in U.S. Pat. Nos. 3,575,328 and 5,441,189, the cutting knife produces a perforated, or only partially severed, line of cut. It has been determined that the unsevered segments or tabs of residual web material depend on the tensile strength of the material. The type of material, the thickness of the material and many other different factors known in the art determine the tensile strength of the material. Accordingly, when the sheet defined by the perforated line of cut is caused to be completely severed by the pulling force imparted by the user, in the case of low tensile strength products this pulling force will be less than the pulling force required for a high tensile strength product.
It has been determined that users pull with a fairly constant pulling force. Therefore, for a given dispenser, products that have a low tensile strength will have a tendency to break early such that the force required to overcome the spring force is insufficient. For the same dispenser, products that have a high tensile strength can cause multiple towel dispensing, because the force exerted would be insufficient to separate the tabs during dispensing. Accordingly, manufacturers are forced to design dispensers that are matched to the tensile strength of the product to be dispensed.
While adjustable cutter are known per se, these cutters are directed to various aspects of the art that are not pertinent to the present invention. Specifically, U.S. Pat. No. 5,975,456 describes an adjustable web cutter, which allows webs to be cut in various lengths, widths and thickness. The blade adjustment mechanism allows a depth of the blade to be adjusted. U.S. Pat. No. 5,868,346 describes an apparatus for severing a web having a cutter bar with a cutter blade that is adjustable relative to core tubes. U.S. Pat. No. 4,846,035 describes an apparatus for cutting bands of wound material. There are two independent blades that are arranged side by side at an angle to each other and have a hinging movement. The cut is made in two stages and leaves a rectilinear cutting line. U.S. Pat. No. 4,316,564 shows a dispenser for sheet material wound on a roll. A distance between walls of the dispenser is adjustable.
Accordingly, there is a need for an adjustable cutter that can be used in a dispenser where the web material is pulled by the user so that various webs of differing tensile strength can be cut using the same dispenser. The present invention seeks to address this need.